Volumetric evaluation of hepatic tumors: multi-vendor, multi-reader liver phantom study

Comparison between CT volumetry and extracellular volume fraction using liver dynamic CT for the predictive ability of liver fibrosis in patients with hepatocellular carcinoma

OBJECTIVES

To compare the predictive ability of liver fibrosis (LF) by CT-volumetry (CTV) for liver and spleen and extracellular volume fraction (ECV) for liver in patients undergoing liver resection.

METHODS

We retrospectively analysed 90 consecutive patients who underwent CTV and ECV. Manually placed region-of-interest ECV (manual-ECV), rigid-registration ECV (rigid-ECV), and nonrigid-registration ECV (nonrigid-ECV) were calculated as ECV(%) = (1-haematocrit) × (ΔHUliver/ΔHUaorta), where ΔHU = subtraction of unenhanced phase from equilibrium phase (240 s). Manual-ECV was compared with CTV for the estimation of LF. The total liver volume to body surface area (TLV/BSA), splenic volume to BSA (SV/BSA), ratio of TLV to SV (TLV/SV), ratio of right liver volume to SV (RV/SV), and liver segmental volume ratio (LSVR) were measured. ROC analyses were performed for ECV and CTV.

RESULTS

After excluding 10 patients, seventy-eight (97.5%) out of 80 patients had a Child-Pugh score of 5 points, and two (2.5%) patients had a Child-Pugh score of 6 points. AUC of ECV showed no significant difference among manual-ECV, rigid-ECV, and nonrigid-ECV. TLV/BSA, SV/BSA, TLV/SV, and RV/SV had a higher correlation with LF grades than manual-ECV. AUC of SV/BSA was significantly higher than that of manual-ECV in F0-1 vs F2-4 and F0-2 vs F3-4. AUC of SV/BSA (0.76-0.83) was higher than that of manual-ECV (0.61-0.75) for all LF grades, although manual-ECV could differentiate between F0-3 and F4 at high AUC (0.75).

CONCLUSIONS

In patients undergoing liver resection, SV/BSA is a better method for estimating severe LF grades, although manual-ECV has the ability to estimate cirrhosis (≥ F4).

KEY POINTS

The splenic volume is a better method for estimating liver fibrosis grades. The extracellular volume fraction is also a candidate for the estimation of severe liver fibrosis.

Volumetric analysis at abdominal CT: oncologic and non-oncologic applications

Volumetric analysis is an objective three-dimensional assessment of a lesion or organ that may more accurately depict the burden of complex objects compared to traditional linear size measurement. Small changes in linear size are amplified by corresponding changes in volume, which could have significant clinical implications. Though early methods of calculating volumes were time-consuming and laborious, multiple software platforms are now available with varying degrees of user-software interaction ranging from manual to fully automated. For the assessment of primary malignancy and metastatic disease, volumetric measurements have shown utility in the evaluation of disease burden prior to and following therapy in a variety of cancers. Additionally, volume can be useful in treatment planning prior to resection or locoregional therapies, particularly for hepatic tumours. The utility of CT volumetry in a wide spectrum of non-oncologic pathology has also been described. While clear advantages exist in certain applications, some data have shown that volume is not always the superior method of size assessment and the associated labor intensity may not be worthwhile. Further, lack of uniformity among software platforms is a challenge to widespread implementation. This review will discuss CT volumetry and its potential oncologic and non-oncologic applications in abdominal imaging, as well as advantages and limitations to this quantitative technique.

The Liver Segmental Volume Ratio for Noninvasive Detection of Cirrhosis: Comparison With Established Linear and Volumetric Measures

OBJECTIVE

The aim of this study was to compare the liver segmental volume ratio (LSVR), a novel volumetric computed tomography measurement, with established linear measurements for differentiating normal from cirrhotic livers.

METHODS

Hepatic volumes were measured using semiautomated software (Liver Analysis Application, Philips IntelliSpace Portal) on contrast-enhanced abdominal computed tomography scans in 312 adults, including 108 patients with end-stage liver disease (mean age, 55 years; 63 men/45 women) and 204 healthy controls (potential renal donors; mean age, 46 years; 82 men/122 women). The LSVR was defined as the volume ratio of Couinaud segments I to III to segments IV to VIII. Linear measures included the caudate-to-right lobe ratio and maximal splenic dimension.

RESULTS

Differences in LSVR between cirrhotics and controls were highly significant (P < 0.0001; mean, 0.55 ± 0.29 versus 0.27 ± 0.07; receiver operating characteristic [ROC] area under the curve [AUC], 0.916). Linear caudate-to-right lobe ratio differences were not statistically significant between the 2 cohorts (P = 0.051; ROC AUC, 0.567). Total liver volume was ineffective for discrimination (ROC AUC, 0.598). An LSVR threshold of 0.35 or greater had a sensitivity and specificity for cirrhosis of 81.5% and 88.7%, respectively.

CONCLUSIONS

Regional hepatic volume changes, as reflected by the LSVR, are more effective than standard linear measures or total liver volume for differentiating cirrhotic from normal livers.

Hepatosplenic volumetric assessment at MDCT for staging liver fibrosis

PURPOSE

To investigate hepatosplenic volumetry at MDCT for non-invasive prediction of hepatic fibrosis.

METHODS

Hepatosplenic volume analysis in 624 patients (mean age, 48.8 years; 311 M/313 F) at MDCT was performed using dedicated software and compared against pathological fibrosis stage (F0 = 374; F1 = 48; F2 = 40; F3 = 65; F4 = 97). The liver segmental volume ratio (LSVR) was defined by Couinaud segments I-III over segments IV-VIII. All pre-cirrhotic fibrosis stages (METAVIR F1-F3) were based on liver biopsy within 1 year of MDCT.

RESULTS

LSVR and total splenic volumes increased with stage of fibrosis, with mean(±SD) values of: F0: 0.26 ± 0.06 and 215.1 ± 88.5 mm³; F1: 0.25 ± 0.08 and 294.8 ± 153.4 mm³; F2: 0.331 ± 0.12 and 291.6 ± 197.1 mm³; F3: 0.39 ± 0.15 and 509.6 ± 402.6 mm³; F4: 0.56 ± 0.30 and 790.7 ± 450.3 mm³, respectively. Total hepatic volumes showed poor discrimination (F0: 1674 ± 320 mm³; F4: 1631 ± 691 mm³). For discriminating advanced fibrosis (≥F3), the ROC AUC values for LSVR, total liver volume, splenic volume and LSVR/spleen combined were 0.863, 0.506, 0.890 and 0.947, respectively.

CONCLUSION

Relative changes in segmental liver volumes and total splenic volume allow for non-invasive staging of hepatic fibrosis, whereas total liver volume is a poor predictor. Unlike liver biopsy or elastography, these CT volumetric biomarkers can be obtained retrospectively on routine scans obtained for other indications.

KEY POINTS

• Regional changes in hepatic volume (LSVR) correlate well with degree of fibrosis. • Total liver volume is a very poor predictor of underlying fibrosis. • Total splenic volume is associated with the degree of hepatic fibrosis. • Hepatosplenic volume assessment is comparable to elastography for staging fibrosis. • Unlike elastography, volumetric analysis can be performed retrospectively.